Els mosquits a Andorra

(ENG) The life cycle of the culicidae consists of four phases: the egg, the larva, the pupa and the adult. Between 100 and 200 eggs are deposited by the female on the water surface or in the immediate vicinity, either isolated or grouped together in naviculae. Generally they are adapted so as to be able to float on water. This is the case for the Culex, Culiseta genus and many others which lay their eggs in naviculae directly on the water, or the Anopheles genus, where the eggs have air bags, which, as with the bags of pollen grain in pine trees, give them a greater floatability. Other species, such as many from the Aedes genus, deposit their eggs in isolation on mud and these adapt to desiccation due to their cuticle being highly resistant to dehydration. These eggs can stay on the ground for several years and a significant amount will remain feasible. The larvae will hatch from the eggs under two conditions: the presence of water and a high enough temperature to allow the complete development of the life cycle. The larvae have an advantageous adaptation which frees them from having to depend on the oxygen dissolved in the water to breathe. Their respiratory system is modified so that the exchange of gases occurs at the end of a structure which opens up at the end of the abdomen and which in the Culicidinae subfamily is an obvious siphon in a tube shape and in the Anophelinae subfamily, is a far more discrete opening at the end of the abdomen. This is an extremely useful adaptation seeing as one of the life conditioning elements in the aquatic environment is the presence of dissolved oxygen in the water. Through being able to capture atmospheric oxygen, mosquito larvae can colonize water with a high content of decomposing organic material, very rich in nourishment but limited in oxygen. For this reason septic tanks can be good breeding areas for mosquitoes. Generally the larvae develop fairly quickly: between four and five days in species adapted to areas with fluctuating conditions and up to ten or fifteen days for species in areas with more stable conditions. The larvae go through four successive growth stages before reaching the pupa phase, the stage in which they remain without nourishment until completing the metamorphosis. After about two days, the pupa will turn into an adult.